Sex Differences in Recombination in Sticklebacks.

Recombination often differs markedly between males and females. Here we present the first analysis of sex-specific recombination in Gasterosteus sticklebacks. Using whole-genome sequencing of 15 crosses between G. aculeatus and G. nipponicus, we localized 698 crossovers with a median resolution of 2.3 kb. We also used a bioinformatic approach to infer historical sex-averaged recombination patterns for both species. Recombination is greater in females than males on all chromosomes, and overall map length is 1.64 times longer in females. The locations of crossovers differ strikingly between sexes. Crossovers cluster toward chromosome ends in males, but are distributed more evenly across chromosomes in females. Suppression of recombination near the centromeres in males causes crossovers to cluster at the ends of long arms in acrocentric chromosomes, and greatly reduces crossing over on short arms. The effect of centromeres on recombination is much weaker in females. Genomic differentiation between G. aculeatus and G. nipponicus is strongly correlated with recombination rate, and patterns of differentiation along chromosomes are strongly influenced by male-specific telomere and centromere effects. We found no evidence for fine-scale correlations between recombination and local gene content in either sex. We discuss hypotheses for the origin of sexual dimorphism in recombination and its consequences for sexually antagonistic selection and sex chromosome evolution

Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2

Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO2. In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35000% for the field along the [1-10] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now.Comment: Phys. Rev. Lett. 111, 056601 (2013

Continuous Transition between Antiferromagnetic Insulator and Paramagnetic Metal in the Pyrochlore Iridate Eu2Ir2O7

Our single crystal study of the magneto-thermal and transport properties of the pyrochlore iridate Eu2Ir2O7 reveals a continuous phase transition from a paramagnetic metal to an antiferromagnetic insulator for a sample with stoichiometry within ~1% resolution. The insulating phase has strong proximity to an antiferromagnetic semimetal, which is stabilized by several % level of the off-stoichiometry. Our observations suggest that in addition to electronic correlation and spin-orbit coupling the magnetic order is essential for opening the charge gap.Comment: 6 pages, 6 figure

The Subaru high-z quasar survey: discovery of faint z~6 quasars

We present the discovery of one or two extremely faint z~6 quasars in 6.5 deg^2 utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z_B) and (z_B-z_R) colors, where z_B and z_R are bandpasses with central wavelengths of 8842A and 9841A, respectively. The color selection can effectively isolate quasars at z~6 from M/L/T dwarfs without the J-band photometry down to z_R<24.0, which is 3.5 mag. deeper than SDSS. We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z=6.156 with M_1450=-23.10. We also identified one possible quasar at z=6.041 with a faint continuum of M_1450=-22.58 and a narrow Lyman-alpha emission with HWHM=427 km/s, which cannot be distinguished from Lyman-alpha emitters. We derive the quasar luminosity function at z~6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower-z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars and several quasar candidates are still remain to be diagnosed. The steepening of the quasar luminosity function at the faint-end does increase the expected emission rate of the ionizing photon, however, it only changes by a factor of ~2-6. This was found to be still insufficient for the required photon budget of reionization at z~6.Comment: 10 pages, 8 figures. Accepted for publication in Ap

Orthogonal magnetization and symmetry breaking in pyrochlore iridate Eu2Ir2O7

Electrons in the pyrochlore iridates experience a large interaction energy in addition to a strong spin-orbit interaction. Both features make the iridates promising for realizing novel states such as the topological Mott insulator.The pyrochlore iridate Eu₂Ir₂O₇ shows a metal-insulator transition at T[subscript N] 1/4 120 K below which a magnetically ordered state develops. Using torque magnetometry, we uncover an unusual magnetic response. A magnetic field H applied in its a-b plane produces a nonlinear magnetization M⊥ orthogonal to the plane. M⊥ displays a d-wave field-angle pattern consistent with octupolar order, with a handedness dictated by field cooling, leading to symmetry breaking of the chirality. A surprise is that the lobe orientation of the d-wave pattern is sensitive to the direction of the field when the sample is field-cooled below T[subscript N], suggestive of an additional order parameter already present at 300 K.National Science Foundation (U.S.) (Grant DMR 1420541)Gordon and Betty Moore Foundation (Grant GBMF4539)United States. Department of Energy (Grant DE-SC0010526

Minor Contribution of Quasars to Ionizing Photon Budget at z~6: Update on Quasar Luminosity Function at the Faint-end with Subaru/Suprime-Cam

We constrain the quasar contribution to cosmic reionization based on our deep optical survey of z~6 quasars down to z_R=24.15 using Subaru/Suprime-Cam in three UKIDSS-DXS fields covering 6.5 deg^2. In Kashikawa et al. (2015), we select 17 quasar candidates and report our initial discovery of two low-luminosity quasars (M_1450~ -23) from seven targets, one of which might be a Lyman alpha emitting galaxy. From an additional optical spectroscopy, none of the four candidates out of the remaining ten turn out to be genuine quasars. Moreover, the deeper optical photometry provided by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) shows that, unlike the two already-known quasars, the i-z and z-y colors of the last six candidates are consistent with M- or L-type brown dwarfs. Therefore, the quasar luminosity function (QLF) in the previous paper is confirmed. Compiling QLF measurements from the literature over a wide magnitude range, including an extremely faint AGN candidate from Parsa et al. (2017}, to fit them with a double power-law, we find that the best-fit faint-end slope is alpha=-2.04^+0.33_-0.18 (-1.98^+0.48_-0.21) and characteristic magnitude is M_1450^*=-25.8^+1.1_-1.9 (-25.7^+1.0_-1.8) in the case of two (one) quasar detection. Our result suggests that, if the QLF is integrated down to M_1450=-18, quasars produce ~1-12% of the ionizing photons required to ionize the whole universe at z~6 with 2sigma confidence level, assuming that the escape fraction is f_esc=1 and the IGM clumpy factor is C=3. Even when the systematic uncertainties are taken into account, our result supports the scenario that quasars are the minor contributors of reionization.Comment: 8 pages, 3 figures, ApJL accepte

The Subaru HSC Galaxy Clustering with Photometric Redshift. I. Dark Halo Masses versus Baryonic Properties of Galaxies at 0.3≤z≤ 1.4

We present the clustering properties of low-$z$ $(z\leq1.4)$ galaxies selected by the Hyper Suprime-Cam Subaru Strategic Program Wide layer over $145$ deg$^{2}$. The wide-field and multi-wavelength observation yields $5,064,770$ galaxies at $0.3\leq z\leq1.4$ with photometric redshifts and physical properties. This enables the accurate measurement of angular correlation functions and subsequent halo occupation distribution (HOD) analysis allows the connection between baryonic properties and dark halo properties. The fraction of less-massive satellite galaxies at $z\lesssim1$ is found to be almost constant at $\sim20\%$, but it gradually decreases beyond $M_{\star} \sim 10^{10.4}h^{-2}M_{\odot}$. However, the abundance of satellite galaxies at $z>1$ is quite small even for less-massive galaxies due to the rarity of massive centrals at high-$z$. This decreasing trend is connected to the small satellite fraction of Lyman break galaxies at $z>3$. The stellar-to-halo mass ratios at $0.3\leq z\leq1.4$ are almost consistent with the predictions obtained using the latest empirical model; however, we identify small excesses from the theoretical model at the massive end. The pivot halo mass is found to be unchanged at $10^{11.9-12.1}h^{-1}M_{\odot}$ at $0.3\leq z\leq1.4$, and we systematically show that $10^{12}h^{-1}M_{\odot}$ is a universal pivot halo mass up to $z\sim5$ that is derived using only the clustering/HOD analyses. Nevertheless, halo masses with peaked instantaneous baryon conversion efficiencies are much smaller than the pivot halo mass regardless of a redshift, and the most efficient stellar-mass assembly is thought to be in progress in $10^{11.0-11.5}h^{-1}M_{\odot}$ dark haloes.Comment: 33 pages, 16 figures, submitted to Ap

On the relation between non-commutative field theories at theta = infinity and large N matrix field theories

It is well-known that non-commutative (NC) field theories at theta = infinity are ``equivalent'' to large N matrix field theories to all orders in perturbation theory, due to the dominance of planar diagrams. By formulating a NC field theory on the lattice non-perturbatively and mapping it onto a twisted reduced model, we point out that the above equivalence does not hold if the translational symmetry of the NC field theory is broken spontaneously. As an example we discuss NC scalar field theory, where such a spontaneous symmetry breakdown has been confirmed by Monte Carlo simulations.Comment: 12 pages, LaTe